gotosocial/vendor/github.com/ugorji/go/codec/decode.go
Tobi Smethurst 98263a7de6
Grand test fixup (#138)
* start fixing up tests

* fix up tests + automate with drone

* fiddle with linting

* messing about with drone.yml

* some more fiddling

* hmmm

* add cache

* add vendor directory

* verbose

* ci updates

* update some little things

* update sig
2021-08-12 21:03:24 +02:00

2350 lines
66 KiB
Go

// Copyright (c) 2012-2020 Ugorji Nwoke. All rights reserved.
// Use of this source code is governed by a MIT license found in the LICENSE file.
package codec
import (
"encoding"
"errors"
"io"
"math"
"reflect"
"strconv"
"time"
)
const msgBadDesc = "unrecognized descriptor byte"
const (
decDefMaxDepth = 1024 // maximum depth
decDefChanCap = 64 // should be large, as cap cannot be expanded
decScratchByteArrayLen = (8 + 2 + 2) * 8 // around cacheLineSize ie ~64, depending on Decoder size
// MARKER: massage decScratchByteArrayLen to ensure xxxDecDriver structs fit within cacheLine*N
// decFailNonEmptyIntf configures whether we error
// when decoding naked into a non-empty interface.
//
// Typically, we cannot decode non-nil stream value into
// nil interface with methods (e.g. io.Reader).
// However, in some scenarios, this should be allowed:
// - MapType
// - SliceType
// - Extensions
//
// Consequently, we should relax this. Put it behind a const flag for now.
decFailNonEmptyIntf = false
// decUseTransient says that we should not use the transient optimization.
//
// There's potential for GC corruption or memory overwrites if transient isn't
// used carefully, so this flag helps turn it off quickly if needed.
//
// Use it everywhere needed so we can completely remove unused code blocks.
decUseTransient = true
)
var (
errNeedMapOrArrayDecodeToStruct = errors.New("only encoded map or array can decode into struct")
errCannotDecodeIntoNil = errors.New("cannot decode into nil")
errExpandSliceCannotChange = errors.New("expand slice: cannot change")
errDecoderNotInitialized = errors.New("Decoder not initialized")
errDecUnreadByteNothingToRead = errors.New("cannot unread - nothing has been read")
errDecUnreadByteLastByteNotRead = errors.New("cannot unread - last byte has not been read")
errDecUnreadByteUnknown = errors.New("cannot unread - reason unknown")
errMaxDepthExceeded = errors.New("maximum decoding depth exceeded")
)
// decByteState tracks where the []byte returned by the last call
// to DecodeBytes or DecodeStringAsByte came from
type decByteState uint8
const (
decByteStateNone decByteState = iota
decByteStateZerocopy // view into []byte that we are decoding from
decByteStateReuseBuf // view into transient buffer used internally by decDriver
// decByteStateNewAlloc
)
type decNotDecodeableReason uint8
const (
decNotDecodeableReasonUnknown decNotDecodeableReason = iota
decNotDecodeableReasonBadKind
decNotDecodeableReasonNonAddrValue
decNotDecodeableReasonNilReference
)
type decDriver interface {
// this will check if the next token is a break.
CheckBreak() bool
// TryNil tries to decode as nil.
// If a nil is in the stream, it consumes it and returns true.
//
// Note: if TryNil returns true, that must be handled.
TryNil() bool
// ContainerType returns one of: Bytes, String, Nil, Slice or Map.
//
// Return unSet if not known.
//
// Note: Implementations MUST fully consume sentinel container types, specifically Nil.
ContainerType() (vt valueType)
// DecodeNaked will decode primitives (number, bool, string, []byte) and RawExt.
// For maps and arrays, it will not do the decoding in-band, but will signal
// the decoder, so that is done later, by setting the fauxUnion.valueType field.
//
// Note: Numbers are decoded as int64, uint64, float64 only (no smaller sized number types).
// for extensions, DecodeNaked must read the tag and the []byte if it exists.
// if the []byte is not read, then kInterfaceNaked will treat it as a Handle
// that stores the subsequent value in-band, and complete reading the RawExt.
//
// extensions should also use readx to decode them, for efficiency.
// kInterface will extract the detached byte slice if it has to pass it outside its realm.
DecodeNaked()
DecodeInt64() (i int64)
DecodeUint64() (ui uint64)
DecodeFloat64() (f float64)
DecodeBool() (b bool)
// DecodeStringAsBytes returns the bytes representing a string.
// It will return a view into scratch buffer or input []byte (if applicable).
//
// Note: This can also decode symbols, if supported.
//
// Users should consume it right away and not store it for later use.
DecodeStringAsBytes() (v []byte)
// DecodeBytes returns the bytes representing a binary value.
// It will return a view into scratch buffer or input []byte (if applicable).
//
// All implementations must honor the contract below:
// if ZeroCopy and applicable, return a view into input []byte we are decoding from
// else if in == nil, return a view into scratch buffer
// else append decoded value to in[:0] and return that
// (this can be simulated by passing []byte{} as in parameter)
//
// Implementations must also update Decoder.decByteState on each call to
// DecodeBytes or DecodeStringAsBytes. Some callers may check that and work appropriately.
//
// Note: DecodeBytes may decode past the length of the passed byte slice, up to the cap.
// Consequently, it is ok to pass a zero-len slice to DecodeBytes, as the returned
// byte slice will have the appropriate length.
DecodeBytes(in []byte) (out []byte)
// DecodeBytes(bs []byte, isstring, zerocopy bool) (bsOut []byte)
// DecodeExt will decode into a *RawExt or into an extension.
DecodeExt(v interface{}, basetype reflect.Type, xtag uint64, ext Ext)
// decodeExt(verifyTag bool, tag byte) (xtag byte, xbs []byte)
DecodeTime() (t time.Time)
// ReadArrayStart will return the length of the array.
// If the format doesn't prefix the length, it returns containerLenUnknown.
// If the expected array was a nil in the stream, it returns containerLenNil.
ReadArrayStart() int
ReadArrayEnd()
// ReadMapStart will return the length of the array.
// If the format doesn't prefix the length, it returns containerLenUnknown.
// If the expected array was a nil in the stream, it returns containerLenNil.
ReadMapStart() int
ReadMapEnd()
reset()
// atEndOfDecode()
// nextValueBytes will return the bytes representing the next value in the stream.
//
// if start is nil, then treat it as a request to discard the next set of bytes,
// and the return response does not matter.
// Typically, this means that the returned []byte is nil/empty/undefined.
//
// Optimize for decoding from a []byte, where the nextValueBytes will just be a sub-slice
// of the input slice. Callers that need to use this to not be a view into the input bytes
// should handle it appropriately.
nextValueBytes(start []byte) []byte
// descBd will describe the token descriptor that signifies what type was decoded
descBd() string
decoder() *Decoder
driverStateManager
decNegintPosintFloatNumber
}
type decDriverContainerTracker interface {
ReadArrayElem()
ReadMapElemKey()
ReadMapElemValue()
}
type decNegintPosintFloatNumber interface {
decInteger() (ui uint64, neg, ok bool)
decFloat() (f float64, ok bool)
}
type decDriverNoopNumberHelper struct{}
func (x decDriverNoopNumberHelper) decInteger() (ui uint64, neg, ok bool) {
panic("decInteger unsupported")
}
func (x decDriverNoopNumberHelper) decFloat() (f float64, ok bool) { panic("decFloat unsupported") }
type decDriverNoopContainerReader struct{}
func (x decDriverNoopContainerReader) ReadArrayStart() (v int) { panic("ReadArrayStart unsupported") }
func (x decDriverNoopContainerReader) ReadArrayEnd() {}
func (x decDriverNoopContainerReader) ReadMapStart() (v int) { panic("ReadMapStart unsupported") }
func (x decDriverNoopContainerReader) ReadMapEnd() {}
func (x decDriverNoopContainerReader) CheckBreak() (v bool) { return }
// DecodeOptions captures configuration options during decode.
type DecodeOptions struct {
// MapType specifies type to use during schema-less decoding of a map in the stream.
// If nil (unset), we default to map[string]interface{} iff json handle and MapKeyAsString=true,
// else map[interface{}]interface{}.
MapType reflect.Type
// SliceType specifies type to use during schema-less decoding of an array in the stream.
// If nil (unset), we default to []interface{} for all formats.
SliceType reflect.Type
// MaxInitLen defines the maxinum initial length that we "make" a collection
// (string, slice, map, chan). If 0 or negative, we default to a sensible value
// based on the size of an element in the collection.
//
// For example, when decoding, a stream may say that it has 2^64 elements.
// We should not auto-matically provision a slice of that size, to prevent Out-Of-Memory crash.
// Instead, we provision up to MaxInitLen, fill that up, and start appending after that.
MaxInitLen int
// ReaderBufferSize is the size of the buffer used when reading.
//
// if > 0, we use a smart buffer internally for performance purposes.
ReaderBufferSize int
// MaxDepth defines the maximum depth when decoding nested
// maps and slices. If 0 or negative, we default to a suitably large number (currently 1024).
MaxDepth int16
// If ErrorIfNoField, return an error when decoding a map
// from a codec stream into a struct, and no matching struct field is found.
ErrorIfNoField bool
// If ErrorIfNoArrayExpand, return an error when decoding a slice/array that cannot be expanded.
// For example, the stream contains an array of 8 items, but you are decoding into a [4]T array,
// or you are decoding into a slice of length 4 which is non-addressable (and so cannot be set).
ErrorIfNoArrayExpand bool
// If SignedInteger, use the int64 during schema-less decoding of unsigned values (not uint64).
SignedInteger bool
// MapValueReset controls how we decode into a map value.
//
// By default, we MAY retrieve the mapping for a key, and then decode into that.
// However, especially with big maps, that retrieval may be expensive and unnecessary
// if the stream already contains all that is necessary to recreate the value.
//
// If true, we will never retrieve the previous mapping,
// but rather decode into a new value and set that in the map.
//
// If false, we will retrieve the previous mapping if necessary e.g.
// the previous mapping is a pointer, or is a struct or array with pre-set state,
// or is an interface.
MapValueReset bool
// SliceElementReset: on decoding a slice, reset the element to a zero value first.
//
// concern: if the slice already contained some garbage, we will decode into that garbage.
SliceElementReset bool
// InterfaceReset controls how we decode into an interface.
//
// By default, when we see a field that is an interface{...},
// or a map with interface{...} value, we will attempt decoding into the
// "contained" value.
//
// However, this prevents us from reading a string into an interface{}
// that formerly contained a number.
//
// If true, we will decode into a new "blank" value, and set that in the interface.
// If false, we will decode into whatever is contained in the interface.
InterfaceReset bool
// InternString controls interning of strings during decoding.
//
// Some handles, e.g. json, typically will read map keys as strings.
// If the set of keys are finite, it may help reduce allocation to
// look them up from a map (than to allocate them afresh).
//
// Note: Handles will be smart when using the intern functionality.
// Every string should not be interned.
// An excellent use-case for interning is struct field names,
// or map keys where key type is string.
InternString bool
// PreferArrayOverSlice controls whether to decode to an array or a slice.
//
// This only impacts decoding into a nil interface{}.
//
// Consequently, it has no effect on codecgen.
//
// *Note*: This only applies if using go1.5 and above,
// as it requires reflect.ArrayOf support which was absent before go1.5.
PreferArrayOverSlice bool
// DeleteOnNilMapValue controls how to decode a nil value in the stream.
//
// If true, we will delete the mapping of the key.
// Else, just set the mapping to the zero value of the type.
//
// Deprecated: This does NOTHING and is left behind for compiling compatibility.
// This change is necessitated because 'nil' in a stream now consistently
// means the zero value (ie reset the value to its zero state).
DeleteOnNilMapValue bool
// RawToString controls how raw bytes in a stream are decoded into a nil interface{}.
// By default, they are decoded as []byte, but can be decoded as string (if configured).
RawToString bool
// ZeroCopy controls whether decoded values of []byte or string type
// point into the input []byte parameter passed to a NewDecoderBytes/ResetBytes(...) call.
//
// To illustrate, if ZeroCopy and decoding from a []byte (not io.Writer),
// then a []byte or string in the output result may just be a slice of (point into)
// the input bytes.
//
// This optimization prevents unnecessary copying.
//
// However, it is made optional, as the caller MUST ensure that the input parameter []byte is
// not modified after the Decode() happens, as any changes are mirrored in the decoded result.
ZeroCopy bool
// PreferPointerForStructOrArray controls whether a struct or array
// is stored in a nil interface{}, or a pointer to it.
//
// This mostly impacts when we decode registered extensions.
PreferPointerForStructOrArray bool
}
// ----------------------------------------
func (d *Decoder) rawExt(f *codecFnInfo, rv reflect.Value) {
d.d.DecodeExt(rv2i(rv), f.ti.rt, 0, nil)
}
func (d *Decoder) ext(f *codecFnInfo, rv reflect.Value) {
d.d.DecodeExt(rv2i(rv), f.ti.rt, f.xfTag, f.xfFn)
}
func (d *Decoder) selferUnmarshal(f *codecFnInfo, rv reflect.Value) {
rv2i(rv).(Selfer).CodecDecodeSelf(d)
}
func (d *Decoder) binaryUnmarshal(f *codecFnInfo, rv reflect.Value) {
bm := rv2i(rv).(encoding.BinaryUnmarshaler)
xbs := d.d.DecodeBytes(nil)
fnerr := bm.UnmarshalBinary(xbs)
d.onerror(fnerr)
}
func (d *Decoder) textUnmarshal(f *codecFnInfo, rv reflect.Value) {
tm := rv2i(rv).(encoding.TextUnmarshaler)
fnerr := tm.UnmarshalText(d.d.DecodeStringAsBytes())
d.onerror(fnerr)
}
func (d *Decoder) jsonUnmarshal(f *codecFnInfo, rv reflect.Value) {
d.jsonUnmarshalV(rv2i(rv).(jsonUnmarshaler))
}
func (d *Decoder) jsonUnmarshalV(tm jsonUnmarshaler) {
// grab the bytes to be read, as UnmarshalJSON needs the full JSON so as to unmarshal it itself.
var bs0 = []byte{}
if !d.bytes {
bs0 = d.blist.get(256)
}
bs := d.d.nextValueBytes(bs0)
fnerr := tm.UnmarshalJSON(bs)
if !d.bytes {
d.blist.put(bs)
if !byteSliceSameData(bs0, bs) {
d.blist.put(bs0)
}
}
d.onerror(fnerr)
}
func (d *Decoder) kErr(f *codecFnInfo, rv reflect.Value) {
d.errorf("no decoding function defined for kind %v", rv.Kind())
}
func (d *Decoder) raw(f *codecFnInfo, rv reflect.Value) {
rvSetBytes(rv, d.rawBytes())
}
func (d *Decoder) kString(f *codecFnInfo, rv reflect.Value) {
rvSetString(rv, d.stringZC(d.d.DecodeStringAsBytes()))
}
func (d *Decoder) kBool(f *codecFnInfo, rv reflect.Value) {
rvSetBool(rv, d.d.DecodeBool())
}
func (d *Decoder) kTime(f *codecFnInfo, rv reflect.Value) {
rvSetTime(rv, d.d.DecodeTime())
}
func (d *Decoder) kFloat32(f *codecFnInfo, rv reflect.Value) {
rvSetFloat32(rv, d.decodeFloat32())
}
func (d *Decoder) kFloat64(f *codecFnInfo, rv reflect.Value) {
rvSetFloat64(rv, d.d.DecodeFloat64())
}
func (d *Decoder) kComplex64(f *codecFnInfo, rv reflect.Value) {
rvSetComplex64(rv, complex(d.decodeFloat32(), 0))
}
func (d *Decoder) kComplex128(f *codecFnInfo, rv reflect.Value) {
rvSetComplex128(rv, complex(d.d.DecodeFloat64(), 0))
}
func (d *Decoder) kInt(f *codecFnInfo, rv reflect.Value) {
rvSetInt(rv, int(chkOvf.IntV(d.d.DecodeInt64(), intBitsize)))
}
func (d *Decoder) kInt8(f *codecFnInfo, rv reflect.Value) {
rvSetInt8(rv, int8(chkOvf.IntV(d.d.DecodeInt64(), 8)))
}
func (d *Decoder) kInt16(f *codecFnInfo, rv reflect.Value) {
rvSetInt16(rv, int16(chkOvf.IntV(d.d.DecodeInt64(), 16)))
}
func (d *Decoder) kInt32(f *codecFnInfo, rv reflect.Value) {
rvSetInt32(rv, int32(chkOvf.IntV(d.d.DecodeInt64(), 32)))
}
func (d *Decoder) kInt64(f *codecFnInfo, rv reflect.Value) {
rvSetInt64(rv, d.d.DecodeInt64())
}
func (d *Decoder) kUint(f *codecFnInfo, rv reflect.Value) {
rvSetUint(rv, uint(chkOvf.UintV(d.d.DecodeUint64(), uintBitsize)))
}
func (d *Decoder) kUintptr(f *codecFnInfo, rv reflect.Value) {
rvSetUintptr(rv, uintptr(chkOvf.UintV(d.d.DecodeUint64(), uintBitsize)))
}
func (d *Decoder) kUint8(f *codecFnInfo, rv reflect.Value) {
rvSetUint8(rv, uint8(chkOvf.UintV(d.d.DecodeUint64(), 8)))
}
func (d *Decoder) kUint16(f *codecFnInfo, rv reflect.Value) {
rvSetUint16(rv, uint16(chkOvf.UintV(d.d.DecodeUint64(), 16)))
}
func (d *Decoder) kUint32(f *codecFnInfo, rv reflect.Value) {
rvSetUint32(rv, uint32(chkOvf.UintV(d.d.DecodeUint64(), 32)))
}
func (d *Decoder) kUint64(f *codecFnInfo, rv reflect.Value) {
rvSetUint64(rv, d.d.DecodeUint64())
}
func (d *Decoder) kInterfaceNaked(f *codecFnInfo) (rvn reflect.Value) {
// nil interface:
// use some hieristics to decode it appropriately
// based on the detected next value in the stream.
n := d.naked()
d.d.DecodeNaked()
// We cannot decode non-nil stream value into nil interface with methods (e.g. io.Reader).
// Howver, it is possible that the user has ways to pass in a type for a given interface
// - MapType
// - SliceType
// - Extensions
//
// Consequently, we should relax this. Put it behind a const flag for now.
if decFailNonEmptyIntf && f.ti.numMeth > 0 {
d.errorf("cannot decode non-nil codec value into nil %v (%v methods)", f.ti.rt, f.ti.numMeth)
}
switch n.v {
case valueTypeMap:
mtid := d.mtid
if mtid == 0 {
if d.jsms { // if json, default to a map type with string keys
mtid = mapStrIntfTypId // for json performance
} else {
mtid = mapIntfIntfTypId
}
}
if mtid == mapStrIntfTypId {
var v2 map[string]interface{}
d.decode(&v2)
rvn = rv4iptr(&v2).Elem()
} else if mtid == mapIntfIntfTypId {
var v2 map[interface{}]interface{}
d.decode(&v2)
rvn = rv4iptr(&v2).Elem()
} else if d.mtr {
rvn = reflect.New(d.h.MapType)
d.decode(rv2i(rvn))
rvn = rvn.Elem()
} else {
rvn = rvZeroAddrK(d.h.MapType, reflect.Map)
d.decodeValue(rvn, nil)
}
case valueTypeArray:
if d.stid == 0 || d.stid == intfSliceTypId {
var v2 []interface{}
d.decode(&v2)
rvn = rv4iptr(&v2).Elem()
} else if d.str {
rvn = reflect.New(d.h.SliceType)
d.decode(rv2i(rvn))
rvn = rvn.Elem()
} else {
rvn = rvZeroAddrK(d.h.SliceType, reflect.Slice)
d.decodeValue(rvn, nil)
}
if reflectArrayOfSupported && d.h.PreferArrayOverSlice {
rvn = rvGetArray4Slice(rvn)
}
case valueTypeExt:
tag, bytes := n.u, n.l // calling decode below might taint the values
bfn := d.h.getExtForTag(tag)
var re = RawExt{Tag: tag}
if bytes == nil {
// it is one of the InterfaceExt ones: json and cbor.
// most likely cbor, as json decoding never reveals valueTypeExt (no tagging support)
if bfn == nil {
d.decode(&re.Value)
rvn = rv4iptr(&re).Elem()
} else {
if bfn.ext == SelfExt {
rvn = rvZeroAddrK(bfn.rt, bfn.rt.Kind())
d.decodeValue(rvn, d.h.fnNoExt(bfn.rt))
} else {
rvn = reflect.New(bfn.rt)
d.interfaceExtConvertAndDecode(rv2i(rvn), bfn.ext)
rvn = rvn.Elem()
}
}
} else {
// one of the BytesExt ones: binc, msgpack, simple
if bfn == nil {
re.setData(bytes, false)
rvn = rv4iptr(&re).Elem()
} else {
rvn = reflect.New(bfn.rt)
if bfn.ext == SelfExt {
d.sideDecode(rv2i(rvn), bfn.rt, bytes)
} else {
bfn.ext.ReadExt(rv2i(rvn), bytes)
}
rvn = rvn.Elem()
}
}
// if struct/array, directly store pointer into the interface
if d.h.PreferPointerForStructOrArray && rvn.CanAddr() {
if rk := rvn.Kind(); rk == reflect.Array || rk == reflect.Struct {
rvn = rvn.Addr()
}
}
case valueTypeNil:
// rvn = reflect.Zero(f.ti.rt)
// no-op
case valueTypeInt:
rvn = n.ri()
case valueTypeUint:
rvn = n.ru()
case valueTypeFloat:
rvn = n.rf()
case valueTypeBool:
rvn = n.rb()
case valueTypeString, valueTypeSymbol:
rvn = n.rs()
case valueTypeBytes:
rvn = n.rl()
case valueTypeTime:
rvn = n.rt()
default:
halt.errorf("kInterfaceNaked: unexpected valueType: %d", n.v)
}
return
}
func (d *Decoder) kInterface(f *codecFnInfo, rv reflect.Value) {
// Note: A consequence of how kInterface works, is that
// if an interface already contains something, we try
// to decode into what was there before.
// We do not replace with a generic value (as got from decodeNaked).
//
// every interface passed here MUST be settable.
//
// ensure you call rvSetIntf(...) before returning.
isnilrv := rvIsNil(rv)
var rvn reflect.Value
if d.h.InterfaceReset {
// check if mapping to a type: if so, initialize it and move on
rvn = d.h.intf2impl(f.ti.rtid)
if !rvn.IsValid() {
rvn = d.kInterfaceNaked(f)
if rvn.IsValid() {
rvSetIntf(rv, rvn)
} else if !isnilrv {
decSetNonNilRV2Zero4Intf(rv)
}
return
}
} else if isnilrv {
// check if mapping to a type: if so, initialize it and move on
rvn = d.h.intf2impl(f.ti.rtid)
if !rvn.IsValid() {
rvn = d.kInterfaceNaked(f)
if rvn.IsValid() {
rvSetIntf(rv, rvn)
}
return
}
} else {
// now we have a non-nil interface value, meaning it contains a type
rvn = rv.Elem()
}
// rvn is now a non-interface type
canDecode, _ := isDecodeable(rvn)
// Note: interface{} is settable, but underlying type may not be.
// Consequently, we MAY have to allocate a value (containing the underlying value),
// decode into it, and reset the interface to that new value.
if !canDecode {
rvn2 := d.oneShotAddrRV(rvType(rvn), rvn.Kind())
rvSetDirect(rvn2, rvn)
rvn = rvn2
}
d.decodeValue(rvn, nil)
rvSetIntf(rv, rvn)
}
func decStructFieldKeyNotString(dd decDriver, keyType valueType, b *[decScratchByteArrayLen]byte) (rvkencname []byte) {
if keyType == valueTypeInt {
rvkencname = strconv.AppendInt(b[:0], dd.DecodeInt64(), 10)
} else if keyType == valueTypeUint {
rvkencname = strconv.AppendUint(b[:0], dd.DecodeUint64(), 10)
} else if keyType == valueTypeFloat {
rvkencname = strconv.AppendFloat(b[:0], dd.DecodeFloat64(), 'f', -1, 64)
} else {
halt.errorf("invalid struct key type: %v", keyType)
}
return
}
func (d *Decoder) kStruct(f *codecFnInfo, rv reflect.Value) {
ctyp := d.d.ContainerType()
ti := f.ti
var mf MissingFielder
if ti.flagMissingFielder {
mf = rv2i(rv).(MissingFielder)
} else if ti.flagMissingFielderPtr {
mf = rv2i(rvAddr(rv, ti.ptr)).(MissingFielder)
}
if ctyp == valueTypeMap {
containerLen := d.mapStart(d.d.ReadMapStart())
if containerLen == 0 {
d.mapEnd()
return
}
hasLen := containerLen >= 0
var name2 []byte
if mf != nil {
var namearr2 [16]byte
name2 = namearr2[:0]
}
var rvkencname []byte
for j := 0; d.containerNext(j, containerLen, hasLen); j++ {
d.mapElemKey()
if ti.keyType == valueTypeString {
rvkencname = d.d.DecodeStringAsBytes()
} else {
rvkencname = decStructFieldKeyNotString(d.d, ti.keyType, &d.b)
}
d.mapElemValue()
if si := ti.siForEncName(rvkencname); si != nil {
d.decodeValue(si.path.fieldAlloc(rv), nil)
} else if mf != nil {
// store rvkencname in new []byte, as it previously shares Decoder.b, which is used in decode
name2 = append(name2[:0], rvkencname...)
var f interface{}
d.decode(&f)
if !mf.CodecMissingField(name2, f) && d.h.ErrorIfNoField {
d.errorf("no matching struct field when decoding stream map with key: %s ", stringView(name2))
}
} else {
d.structFieldNotFound(-1, stringView(rvkencname))
}
}
d.mapEnd()
} else if ctyp == valueTypeArray {
containerLen := d.arrayStart(d.d.ReadArrayStart())
if containerLen == 0 {
d.arrayEnd()
return
}
// Not much gain from doing it two ways for array.
// Arrays are not used as much for structs.
hasLen := containerLen >= 0
var checkbreak bool
tisfi := ti.sfi.source()
for j, si := range tisfi {
if hasLen {
if j == containerLen {
break
}
} else if d.checkBreak() {
checkbreak = true
break
}
d.arrayElem()
d.decodeValue(si.path.fieldAlloc(rv), nil)
}
var proceed bool
if hasLen {
proceed = containerLen > len(tisfi)
} else {
proceed = !checkbreak
}
// if (hasLen && containerLen > len(tisfi)) || (!hasLen && !checkbreak) {
if proceed {
// read remaining values and throw away
for j := len(tisfi); ; j++ {
if !d.containerNext(j, containerLen, hasLen) {
break
}
d.arrayElem()
d.structFieldNotFound(j, "")
}
}
d.arrayEnd()
} else {
d.onerror(errNeedMapOrArrayDecodeToStruct)
}
}
func (d *Decoder) kSlice(f *codecFnInfo, rv reflect.Value) {
// A slice can be set from a map or array in stream.
// This way, the order can be kept (as order is lost with map).
// Note: rv is a slice type here - guaranteed
ti := f.ti
rvCanset := rv.CanSet()
ctyp := d.d.ContainerType()
if ctyp == valueTypeBytes || ctyp == valueTypeString {
// you can only decode bytes or string in the stream into a slice or array of bytes
if !(ti.rtid == uint8SliceTypId || ti.elemkind == uint8(reflect.Uint8)) {
d.errorf("bytes/string in stream must decode into slice/array of bytes, not %v", ti.rt)
}
rvbs := rvGetBytes(rv)
if !rvCanset {
// not addressable byte slice, so do not decode into it past the length
rvbs = rvbs[:len(rvbs):len(rvbs)]
}
bs2 := d.decodeBytesInto(rvbs)
// if !(len(bs2) == len(rvbs) && byteSliceSameData(rvbs, bs2)) {
if !(len(bs2) > 0 && len(bs2) == len(rvbs) && &bs2[0] == &rvbs[0]) {
if rvCanset {
rvSetBytes(rv, bs2)
} else if len(rvbs) > 0 && len(bs2) > 0 {
copy(rvbs, bs2)
}
}
return
}
slh, containerLenS := d.decSliceHelperStart() // only expects valueType(Array|Map) - never Nil
// an array can never return a nil slice. so no need to check f.array here.
if containerLenS == 0 {
if rvCanset {
if rvIsNil(rv) {
rvSetDirect(rv, rvSliceZeroCap(ti.rt))
} else {
rvSetSliceLen(rv, 0)
}
}
slh.End()
return
}
rtelem0Mut := !scalarBitset.isset(ti.elemkind)
rtelem := ti.elem
for k := reflect.Kind(ti.elemkind); k == reflect.Ptr; k = rtelem.Kind() {
rtelem = rtelem.Elem()
}
var fn *codecFn
var rvChanged bool
var rv0 = rv
var rv9 reflect.Value
rvlen := rvLenSlice(rv)
rvcap := rvCapSlice(rv)
hasLen := containerLenS > 0
if hasLen {
if containerLenS > rvcap {
oldRvlenGtZero := rvlen > 0
rvlen1 := decInferLen(containerLenS, d.h.MaxInitLen, int(ti.elemsize))
if rvlen1 == rvlen {
} else if rvlen1 <= rvcap {
if rvCanset {
rvlen = rvlen1
rvSetSliceLen(rv, rvlen)
}
} else if rvCanset { // rvlen1 > rvcap
rvlen = rvlen1
rv, rvCanset = rvMakeSlice(rv, f.ti, rvlen, rvlen)
rvcap = rvlen
rvChanged = !rvCanset
} else { // rvlen1 > rvcap && !canSet
d.errorf("cannot decode into non-settable slice")
}
if rvChanged && oldRvlenGtZero && rtelem0Mut {
rvCopySlice(rv, rv0, rtelem) // only copy up to length NOT cap i.e. rv0.Slice(0, rvcap)
}
} else if containerLenS != rvlen {
if rvCanset {
rvlen = containerLenS
rvSetSliceLen(rv, rvlen)
}
}
}
// consider creating new element once, and just decoding into it.
var elemReset = d.h.SliceElementReset
var j int
for ; d.containerNext(j, containerLenS, hasLen); j++ {
if j == 0 {
if rvIsNil(rv) { // means hasLen = false
if rvCanset {
rvlen = decInferLen(containerLenS, d.h.MaxInitLen, int(ti.elemsize))
rv, rvCanset = rvMakeSlice(rv, f.ti, rvlen, rvlen)
rvcap = rvlen
rvChanged = !rvCanset
} else {
d.errorf("cannot decode into non-settable slice")
}
}
if fn == nil {
fn = d.h.fn(rtelem)
}
}
// if indefinite, etc, then expand the slice if necessary
if j >= rvlen {
slh.ElemContainerState(j)
// expand the slice up to the cap.
// Note that we did, so we have to reset it later.
if rvlen < rvcap {
rvlen = rvcap
if rvCanset {
rvSetSliceLen(rv, rvlen)
} else if rvChanged {
rv = rvSlice(rv, rvlen)
} else {
d.onerror(errExpandSliceCannotChange)
}
} else {
if !(rvCanset || rvChanged) {
d.onerror(errExpandSliceCannotChange)
}
rv, rvcap, rvCanset = rvGrowSlice(rv, f.ti, rvcap, 1)
rvlen = rvcap
rvChanged = !rvCanset
}
} else {
slh.ElemContainerState(j)
}
rv9 = rvSliceIndex(rv, j, f.ti)
if elemReset {
rvSetZero(rv9)
}
d.decodeValue(rv9, fn)
}
if j < rvlen {
if rvCanset {
rvSetSliceLen(rv, j)
} else if rvChanged {
rv = rvSlice(rv, j)
}
// rvlen = j
} else if j == 0 && rvIsNil(rv) {
if rvCanset {
rv = rvSliceZeroCap(ti.rt)
rvCanset = false
rvChanged = true
}
}
slh.End()
if rvChanged { // infers rvCanset=true, so it can be reset
rvSetDirect(rv0, rv)
}
}
func (d *Decoder) kArray(f *codecFnInfo, rv reflect.Value) {
// An array can be set from a map or array in stream.
ctyp := d.d.ContainerType()
if handleBytesWithinKArray && (ctyp == valueTypeBytes || ctyp == valueTypeString) {
// you can only decode bytes or string in the stream into a slice or array of bytes
if f.ti.elemkind != uint8(reflect.Uint8) {
d.errorf("bytes/string in stream can decode into array of bytes, but not %v", f.ti.rt)
}
rvbs := rvGetArrayBytes(rv, nil)
bs2 := d.decodeBytesInto(rvbs)
if !byteSliceSameData(rvbs, bs2) && len(rvbs) > 0 && len(bs2) > 0 {
copy(rvbs, bs2)
}
return
}
slh, containerLenS := d.decSliceHelperStart() // only expects valueType(Array|Map) - never Nil
// an array can never return a nil slice. so no need to check f.array here.
if containerLenS == 0 {
slh.End()
return
}
rtelem := f.ti.elem
for k := reflect.Kind(f.ti.elemkind); k == reflect.Ptr; k = rtelem.Kind() {
rtelem = rtelem.Elem()
}
var fn *codecFn
var rv9 reflect.Value
rvlen := rv.Len() // same as cap
hasLen := containerLenS > 0
if hasLen && containerLenS > rvlen {
d.errorf("cannot decode into array with length: %v, less than container length: %v", rvlen, containerLenS)
}
// consider creating new element once, and just decoding into it.
var elemReset = d.h.SliceElementReset
for j := 0; d.containerNext(j, containerLenS, hasLen); j++ {
// note that you cannot expand the array if indefinite and we go past array length
if j >= rvlen {
slh.arrayCannotExpand(hasLen, rvlen, j, containerLenS)
return
}
slh.ElemContainerState(j)
rv9 = rvArrayIndex(rv, j, f.ti)
if elemReset {
rvSetZero(rv9)
}
if fn == nil {
fn = d.h.fn(rtelem)
}
d.decodeValue(rv9, fn)
}
slh.End()
}
func (d *Decoder) kChan(f *codecFnInfo, rv reflect.Value) {
// A slice can be set from a map or array in stream.
// This way, the order can be kept (as order is lost with map).
ti := f.ti
if ti.chandir&uint8(reflect.SendDir) == 0 {
d.errorf("receive-only channel cannot be decoded")
}
ctyp := d.d.ContainerType()
if ctyp == valueTypeBytes || ctyp == valueTypeString {
// you can only decode bytes or string in the stream into a slice or array of bytes
if !(ti.rtid == uint8SliceTypId || ti.elemkind == uint8(reflect.Uint8)) {
d.errorf("bytes/string in stream must decode into slice/array of bytes, not %v", ti.rt)
}
bs2 := d.d.DecodeBytes(nil)
irv := rv2i(rv)
ch, ok := irv.(chan<- byte)
if !ok {
ch = irv.(chan byte)
}
for _, b := range bs2 {
ch <- b
}
return
}
var rvCanset = rv.CanSet()
// only expects valueType(Array|Map - nil handled above)
slh, containerLenS := d.decSliceHelperStart()
// an array can never return a nil slice. so no need to check f.array here.
if containerLenS == 0 {
if rvCanset && rvIsNil(rv) {
rvSetDirect(rv, reflect.MakeChan(ti.rt, 0))
}
slh.End()
return
}
rtelem := ti.elem
useTransient := decUseTransient && ti.elemkind != byte(reflect.Ptr) && ti.tielem.flagCanTransient
for k := reflect.Kind(ti.elemkind); k == reflect.Ptr; k = rtelem.Kind() {
rtelem = rtelem.Elem()
}
var fn *codecFn
var rvChanged bool
var rv0 = rv
var rv9 reflect.Value
var rvlen int // = rv.Len()
hasLen := containerLenS > 0
for j := 0; d.containerNext(j, containerLenS, hasLen); j++ {
if j == 0 {
if rvIsNil(rv) {
if hasLen {
rvlen = decInferLen(containerLenS, d.h.MaxInitLen, int(ti.elemsize))
} else {
rvlen = decDefChanCap
}
if rvCanset {
rv = reflect.MakeChan(ti.rt, rvlen)
rvChanged = true
} else {
d.errorf("cannot decode into non-settable chan")
}
}
if fn == nil {
fn = d.h.fn(rtelem)
}
}
slh.ElemContainerState(j)
if rv9.IsValid() {
rvSetZero(rv9)
} else if decUseTransient && useTransient {
rv9 = d.perType.TransientAddrK(ti.elem, reflect.Kind(ti.elemkind))
} else {
rv9 = rvZeroAddrK(ti.elem, reflect.Kind(ti.elemkind))
}
if !d.d.TryNil() {
d.decodeValueNoCheckNil(rv9, fn)
}
rv.Send(rv9)
}
slh.End()
if rvChanged { // infers rvCanset=true, so it can be reset
rvSetDirect(rv0, rv)
}
}
func (d *Decoder) kMap(f *codecFnInfo, rv reflect.Value) {
containerLen := d.mapStart(d.d.ReadMapStart())
ti := f.ti
if rvIsNil(rv) {
rvlen := decInferLen(containerLen, d.h.MaxInitLen, int(ti.keysize+ti.elemsize))
rvSetDirect(rv, makeMapReflect(ti.rt, rvlen))
}
if containerLen == 0 {
d.mapEnd()
return
}
ktype, vtype := ti.key, ti.elem
ktypeId := rt2id(ktype)
vtypeKind := reflect.Kind(ti.elemkind)
ktypeKind := reflect.Kind(ti.keykind)
kfast := mapKeyFastKindFor(ktypeKind)
visindirect := mapStoresElemIndirect(uintptr(ti.elemsize))
visref := refBitset.isset(ti.elemkind)
vtypePtr := vtypeKind == reflect.Ptr
ktypePtr := ktypeKind == reflect.Ptr
vTransient := decUseTransient && !vtypePtr && ti.tielem.flagCanTransient
kTransient := decUseTransient && !ktypePtr && ti.tikey.flagCanTransient
var vtypeElem reflect.Type
var keyFn, valFn *codecFn
var ktypeLo, vtypeLo = ktype, vtype
if ktypeKind == reflect.Ptr {
for ktypeLo = ktype.Elem(); ktypeLo.Kind() == reflect.Ptr; ktypeLo = ktypeLo.Elem() {
}
}
if vtypePtr {
vtypeElem = vtype.Elem()
for vtypeLo = vtypeElem; vtypeLo.Kind() == reflect.Ptr; vtypeLo = vtypeLo.Elem() {
}
}
rvkMut := !scalarBitset.isset(ti.keykind) // if ktype is immutable, then re-use the same rvk.
rvvMut := !scalarBitset.isset(ti.elemkind)
rvvCanNil := isnilBitset.isset(ti.elemkind)
// rvk: key
// rvkn: if non-mutable, on each iteration of loop, set rvk to this
// rvv: value
// rvvn: if non-mutable, on each iteration of loop, set rvv to this
// if mutable, may be used as a temporary value for local-scoped operations
// rvva: if mutable, used as transient value for use for key lookup
// rvvz: zero value of map value type, used to do a map set when nil is found in stream
var rvk, rvkn, rvv, rvvn, rvva, rvvz reflect.Value
// we do a doMapGet if kind is mutable, and InterfaceReset=true if interface
var doMapGet, doMapSet bool
if !d.h.MapValueReset {
if rvvMut && (vtypeKind != reflect.Interface || !d.h.InterfaceReset) {
doMapGet = true
rvva = mapAddrLoopvarRV(vtype, vtypeKind)
}
}
ktypeIsString := ktypeId == stringTypId
ktypeIsIntf := ktypeId == intfTypId
hasLen := containerLen > 0
// kstrbs is used locally for the key bytes, so we can reduce allocation.
// When we read keys, we copy to this local bytes array, and use a stringView for lookup.
// We only convert it into a true string if we have to do a set on the map.
// Since kstr2bs will usually escape to the heap, declaring a [64]byte array may be wasteful.
// It is only valuable if we are sure that it is declared on the stack.
// var kstrarr [64]byte // most keys are less than 32 bytes, and even more less than 64
// var kstrbs = kstrarr[:0]
var kstrbs []byte
var kstr2bs []byte
var s string
var callFnRvk bool
fnRvk2 := func() (s string) {
callFnRvk = false
if len(kstr2bs) < 2 {
return string(kstr2bs)
}
return d.mapKeyString(&callFnRvk, &kstrbs, &kstr2bs)
}
// Use a possibly transient (map) value (and key), to reduce allocation
for j := 0; d.containerNext(j, containerLen, hasLen); j++ {
callFnRvk = false
if j == 0 {
// if vtypekind is a scalar and thus value will be decoded using TransientAddrK,
// then it is ok to use TransientAddr2K for the map key.
if decUseTransient && vTransient && kTransient {
rvk = d.perType.TransientAddr2K(ktype, ktypeKind)
} else {
rvk = rvZeroAddrK(ktype, ktypeKind)
}
if !rvkMut {
rvkn = rvk
}
if !rvvMut {
if decUseTransient && vTransient {
rvvn = d.perType.TransientAddrK(vtype, vtypeKind)
} else {
rvvn = rvZeroAddrK(vtype, vtypeKind)
}
}
if !ktypeIsString && keyFn == nil {
keyFn = d.h.fn(ktypeLo)
}
if valFn == nil {
valFn = d.h.fn(vtypeLo)
}
} else if rvkMut {
rvSetZero(rvk)
} else {
rvk = rvkn
}
d.mapElemKey()
if ktypeIsString {
kstr2bs = d.d.DecodeStringAsBytes()
rvSetString(rvk, fnRvk2())
} else {
d.decByteState = decByteStateNone
d.decodeValue(rvk, keyFn)
// special case if interface wrapping a byte slice
if ktypeIsIntf {
if rvk2 := rvk.Elem(); rvk2.IsValid() && rvType(rvk2) == uint8SliceTyp {
kstr2bs = rvGetBytes(rvk2)
rvSetIntf(rvk, rv4istr(fnRvk2()))
}
// NOTE: consider failing early if map/slice/func
}
}
d.mapElemValue()
if d.d.TryNil() {
// since a map, we have to set zero value if needed
if !rvvz.IsValid() {
rvvz = rvZeroK(vtype, vtypeKind)
}
if callFnRvk {
s = d.string(kstr2bs)
if ktypeIsString {
rvSetString(rvk, s)
} else { // ktypeIsIntf
rvSetIntf(rvk, rv4istr(s))
}
}
mapSet(rv, rvk, rvvz, kfast, visindirect, visref)
continue
}
// there is non-nil content in the stream to decode ...
// consequently, it's ok to just directly create new value to the pointer (if vtypePtr)
// set doMapSet to false iff u do a get, and the return value is a non-nil pointer
doMapSet = true
if !rvvMut {
rvv = rvvn
} else if !doMapGet {
goto NEW_RVV
} else {
rvv = mapGet(rv, rvk, rvva, kfast, visindirect, visref)
if !rvv.IsValid() || (rvvCanNil && rvIsNil(rvv)) {
goto NEW_RVV
}
switch vtypeKind {
case reflect.Ptr, reflect.Map: // ok to decode directly into map
doMapSet = false
case reflect.Interface:
// if an interface{}, just decode into it iff a non-nil ptr/map, else allocate afresh
rvvn = rvv.Elem()
if k := rvvn.Kind(); (k == reflect.Ptr || k == reflect.Map) && !rvIsNil(rvvn) {
d.decodeValueNoCheckNil(rvvn, nil) // valFn is incorrect here
continue
}
// make addressable (so we can set the interface)
rvvn = rvZeroAddrK(vtype, vtypeKind)
rvSetIntf(rvvn, rvv)
rvv = rvvn
default:
// make addressable (so you can set the slice/array elements, etc)
if decUseTransient && vTransient {
rvvn = d.perType.TransientAddrK(vtype, vtypeKind)
} else {
rvvn = rvZeroAddrK(vtype, vtypeKind)
}
rvSetDirect(rvvn, rvv)
rvv = rvvn
}
}
goto DECODE_VALUE_NO_CHECK_NIL
NEW_RVV:
if vtypePtr {
rvv = reflect.New(vtypeElem) // non-nil in stream, so allocate value
} else if decUseTransient && vTransient {
rvv = d.perType.TransientAddrK(vtype, vtypeKind)
} else {
rvv = rvZeroAddrK(vtype, vtypeKind)
}
DECODE_VALUE_NO_CHECK_NIL:
d.decodeValueNoCheckNil(rvv, valFn)
if doMapSet {
if callFnRvk {
s = d.string(kstr2bs)
if ktypeIsString {
rvSetString(rvk, s)
} else { // ktypeIsIntf
rvSetIntf(rvk, rv4istr(s))
}
}
mapSet(rv, rvk, rvv, kfast, visindirect, visref)
}
}
d.mapEnd()
}
// Decoder reads and decodes an object from an input stream in a supported format.
//
// Decoder is NOT safe for concurrent use i.e. a Decoder cannot be used
// concurrently in multiple goroutines.
//
// However, as Decoder could be allocation heavy to initialize, a Reset method is provided
// so its state can be reused to decode new input streams repeatedly.
// This is the idiomatic way to use.
type Decoder struct {
panicHdl
d decDriver
// cache the mapTypeId and sliceTypeId for faster comparisons
mtid uintptr
stid uintptr
h *BasicHandle
blist bytesFreelist
// ---- cpu cache line boundary?
decRd
// ---- cpu cache line boundary?
n fauxUnion
hh Handle
err error
perType decPerType
// used for interning strings
is internerMap
// ---- cpu cache line boundary?
// ---- writable fields during execution --- *try* to keep in sep cache line
maxdepth int16
depth int16
// Extensions can call Decode() within a current Decode() call.
// We need to know when the top level Decode() call returns,
// so we can decide whether to Release() or not.
calls uint16 // what depth in mustDecode are we in now.
c containerState
decByteState
// b is an always-available scratch buffer used by Decoder and decDrivers.
// By being always-available, it can be used for one-off things without
// having to get from freelist, use, and return back to freelist.
b [decScratchByteArrayLen]byte
}
// NewDecoder returns a Decoder for decoding a stream of bytes from an io.Reader.
//
// For efficiency, Users are encouraged to configure ReaderBufferSize on the handle
// OR pass in a memory buffered reader (eg bufio.Reader, bytes.Buffer).
func NewDecoder(r io.Reader, h Handle) *Decoder {
d := h.newDecDriver().decoder()
if r != nil {
d.Reset(r)
}
return d
}
// NewDecoderBytes returns a Decoder which efficiently decodes directly
// from a byte slice with zero copying.
func NewDecoderBytes(in []byte, h Handle) *Decoder {
d := h.newDecDriver().decoder()
if in != nil {
d.ResetBytes(in)
}
return d
}
// NewDecoderString returns a Decoder which efficiently decodes directly
// from a string with zero copying.
//
// It is a convenience function that calls NewDecoderBytes with a
// []byte view into the string.
//
// This can be an efficient zero-copy if using default mode i.e. without codec.safe tag.
func NewDecoderString(s string, h Handle) *Decoder {
return NewDecoderBytes(bytesView(s), h)
}
func (d *Decoder) r() *decRd {
return &d.decRd
}
func (d *Decoder) init(h Handle) {
initHandle(h)
d.bytes = true
d.err = errDecoderNotInitialized
d.h = h.getBasicHandle()
d.hh = h
d.be = h.isBinary()
if d.h.InternString && d.is == nil {
d.is.init()
}
// NOTE: do not initialize d.n here. It is lazily initialized in d.naked()
}
func (d *Decoder) resetCommon() {
d.d.reset()
d.err = nil
d.c = 0
d.decByteState = decByteStateNone
d.depth = 0
d.calls = 0
// reset all things which were cached from the Handle, but could change
d.maxdepth = decDefMaxDepth
if d.h.MaxDepth > 0 {
d.maxdepth = d.h.MaxDepth
}
d.mtid = 0
d.stid = 0
d.mtr = false
d.str = false
if d.h.MapType != nil {
d.mtid = rt2id(d.h.MapType)
d.mtr = fastpathAvIndex(d.mtid) != -1
}
if d.h.SliceType != nil {
d.stid = rt2id(d.h.SliceType)
d.str = fastpathAvIndex(d.stid) != -1
}
}
// Reset the Decoder with a new Reader to decode from,
// clearing all state from last run(s).
func (d *Decoder) Reset(r io.Reader) {
if r == nil {
r = &eofReader
}
d.bytes = false
if d.h.ReaderBufferSize > 0 {
if d.bi == nil {
d.bi = new(bufioDecReader)
}
d.bi.reset(r, d.h.ReaderBufferSize, &d.blist)
d.bufio = true
d.decReader = d.bi
} else {
if d.ri == nil {
d.ri = new(ioDecReader)
}
d.ri.reset(r, &d.blist)
d.bufio = false
d.decReader = d.ri
}
d.resetCommon()
}
// ResetBytes resets the Decoder with a new []byte to decode from,
// clearing all state from last run(s).
func (d *Decoder) ResetBytes(in []byte) {
if in == nil {
in = []byte{}
}
d.bufio = false
d.bytes = true
d.decReader = &d.rb
d.rb.reset(in)
d.resetCommon()
}
// ResetString resets the Decoder with a new string to decode from,
// clearing all state from last run(s).
//
// It is a convenience function that calls ResetBytes with a
// []byte view into the string.
//
// This can be an efficient zero-copy if using default mode i.e. without codec.safe tag.
func (d *Decoder) ResetString(s string) {
d.ResetBytes(bytesView(s))
}
func (d *Decoder) naked() *fauxUnion {
return &d.n
}
// Decode decodes the stream from reader and stores the result in the
// value pointed to by v. v cannot be a nil pointer. v can also be
// a reflect.Value of a pointer.
//
// Note that a pointer to a nil interface is not a nil pointer.
// If you do not know what type of stream it is, pass in a pointer to a nil interface.
// We will decode and store a value in that nil interface.
//
// Sample usages:
// // Decoding into a non-nil typed value
// var f float32
// err = codec.NewDecoder(r, handle).Decode(&f)
//
// // Decoding into nil interface
// var v interface{}
// dec := codec.NewDecoder(r, handle)
// err = dec.Decode(&v)
//
// When decoding into a nil interface{}, we will decode into an appropriate value based
// on the contents of the stream:
// - Numbers are decoded as float64, int64 or uint64.
// - Other values are decoded appropriately depending on the type:
// bool, string, []byte, time.Time, etc
// - Extensions are decoded as RawExt (if no ext function registered for the tag)
// Configurations exist on the Handle to override defaults
// (e.g. for MapType, SliceType and how to decode raw bytes).
//
// When decoding into a non-nil interface{} value, the mode of encoding is based on the
// type of the value. When a value is seen:
// - If an extension is registered for it, call that extension function
// - If it implements BinaryUnmarshaler, call its UnmarshalBinary(data []byte) error
// - Else decode it based on its reflect.Kind
//
// There are some special rules when decoding into containers (slice/array/map/struct).
// Decode will typically use the stream contents to UPDATE the container i.e. the values
// in these containers will not be zero'ed before decoding.
// - A map can be decoded from a stream map, by updating matching keys.
// - A slice can be decoded from a stream array,
// by updating the first n elements, where n is length of the stream.
// - A slice can be decoded from a stream map, by decoding as if
// it contains a sequence of key-value pairs.
// - A struct can be decoded from a stream map, by updating matching fields.
// - A struct can be decoded from a stream array,
// by updating fields as they occur in the struct (by index).
//
// This in-place update maintains consistency in the decoding philosophy (i.e. we ALWAYS update
// in place by default). However, the consequence of this is that values in slices or maps
// which are not zero'ed before hand, will have part of the prior values in place after decode
// if the stream doesn't contain an update for those parts.
//
// This in-place update can be disabled by configuring the MapValueReset and SliceElementReset
// decode options available on every handle.
//
// Furthermore, when decoding a stream map or array with length of 0 into a nil map or slice,
// we reset the destination map or slice to a zero-length value.
//
// However, when decoding a stream nil, we reset the destination container
// to its "zero" value (e.g. nil for slice/map, etc).
//
// Note: we allow nil values in the stream anywhere except for map keys.
// A nil value in the encoded stream where a map key is expected is treated as an error.
func (d *Decoder) Decode(v interface{}) (err error) {
// tried to use closure, as runtime optimizes defer with no params.
// This seemed to be causing weird issues (like circular reference found, unexpected panic, etc).
// Also, see https://github.com/golang/go/issues/14939#issuecomment-417836139
if !debugging {
defer func() {
if x := recover(); x != nil {
panicValToErr(d, x, &d.err)
err = d.err
}
}()
}
d.MustDecode(v)
return
}
// MustDecode is like Decode, but panics if unable to Decode.
//
// Note: This provides insight to the code location that triggered the error.
func (d *Decoder) MustDecode(v interface{}) {
halt.onerror(d.err)
if d.hh == nil {
halt.onerror(errNoFormatHandle)
}
// Top-level: v is a pointer and not nil.
d.calls++
d.decode(v)
d.calls--
}
// Release releases shared (pooled) resources.
//
// It is important to call Release() when done with a Decoder, so those resources
// are released instantly for use by subsequently created Decoders.
//
// By default, Release() is automatically called unless the option ExplicitRelease is set.
//
// Deprecated: Release is a no-op as pooled resources are not used with an Decoder.
// This method is kept for compatibility reasons only.
func (d *Decoder) Release() {
}
func (d *Decoder) swallow() {
d.d.nextValueBytes(nil)
}
func (d *Decoder) swallowErr() (err error) {
if !debugging {
defer func() {
if x := recover(); x != nil {
panicValToErr(d, x, &err)
}
}()
}
d.swallow()
return
}
func setZero(iv interface{}) {
if iv == nil {
return
}
rv, ok := isNil(iv)
if ok {
return
}
// var canDecode bool
switch v := iv.(type) {
case *string:
*v = ""
case *bool:
*v = false
case *int:
*v = 0
case *int8:
*v = 0
case *int16:
*v = 0
case *int32:
*v = 0
case *int64:
*v = 0
case *uint:
*v = 0
case *uint8:
*v = 0
case *uint16:
*v = 0
case *uint32:
*v = 0
case *uint64:
*v = 0
case *float32:
*v = 0
case *float64:
*v = 0
case *complex64:
*v = 0
case *complex128:
*v = 0
case *[]byte:
*v = nil
case *Raw:
*v = nil
case *time.Time:
*v = time.Time{}
case reflect.Value:
decSetNonNilRV2Zero(v)
default:
if !fastpathDecodeSetZeroTypeSwitch(iv) {
decSetNonNilRV2Zero(rv)
}
}
}
// decSetNonNilRV2Zero will set the non-nil value to its zero value.
func decSetNonNilRV2Zero(v reflect.Value) {
// If not decodeable (settable), we do not touch it.
// We considered empty'ing it if not decodeable e.g.
// - if chan, drain it
// - if map, clear it
// - if slice or array, zero all elements up to len
//
// However, we decided instead that we either will set the
// whole value to the zero value, or leave AS IS.
k := v.Kind()
if k == reflect.Interface {
decSetNonNilRV2Zero4Intf(v)
} else if k == reflect.Ptr {
decSetNonNilRV2Zero4Ptr(v)
} else if v.CanSet() {
rvSetDirectZero(v)
}
}
func decSetNonNilRV2Zero4Ptr(v reflect.Value) {
ve := v.Elem()
if ve.CanSet() {
rvSetZero(ve) // we can have a pointer to an interface
} else if v.CanSet() {
rvSetZero(v)
}
}
func decSetNonNilRV2Zero4Intf(v reflect.Value) {
ve := v.Elem()
if ve.CanSet() {
rvSetDirectZero(ve) // interfaces always have element as a non-interface
} else if v.CanSet() {
rvSetZero(v)
}
}
func (d *Decoder) decode(iv interface{}) {
// a switch with only concrete types can be optimized.
// consequently, we deal with nil and interfaces outside the switch.
if iv == nil {
d.onerror(errCannotDecodeIntoNil)
}
switch v := iv.(type) {
// case nil:
// case Selfer:
case reflect.Value:
if x, _ := isDecodeable(v); !x {
d.haltAsNotDecodeable(v)
}
d.decodeValue(v, nil)
case *string:
*v = d.stringZC(d.d.DecodeStringAsBytes())
case *bool:
*v = d.d.DecodeBool()
case *int:
*v = int(chkOvf.IntV(d.d.DecodeInt64(), intBitsize))
case *int8:
*v = int8(chkOvf.IntV(d.d.DecodeInt64(), 8))
case *int16:
*v = int16(chkOvf.IntV(d.d.DecodeInt64(), 16))
case *int32:
*v = int32(chkOvf.IntV(d.d.DecodeInt64(), 32))
case *int64:
*v = d.d.DecodeInt64()
case *uint:
*v = uint(chkOvf.UintV(d.d.DecodeUint64(), uintBitsize))
case *uint8:
*v = uint8(chkOvf.UintV(d.d.DecodeUint64(), 8))
case *uint16:
*v = uint16(chkOvf.UintV(d.d.DecodeUint64(), 16))
case *uint32:
*v = uint32(chkOvf.UintV(d.d.DecodeUint64(), 32))
case *uint64:
*v = d.d.DecodeUint64()
case *float32:
*v = d.decodeFloat32()
case *float64:
*v = d.d.DecodeFloat64()
case *complex64:
*v = complex(d.decodeFloat32(), 0)
case *complex128:
*v = complex(d.d.DecodeFloat64(), 0)
case *[]byte:
*v = d.decodeBytesInto(*v)
case []byte:
// not addressable byte slice, so do not decode into it past the length
b := d.decodeBytesInto(v[:len(v):len(v)])
if !(len(b) > 0 && len(b) == len(v) && &b[0] == &v[0]) { // not same slice
copy(v, b)
}
case *time.Time:
*v = d.d.DecodeTime()
case *Raw:
*v = d.rawBytes()
case *interface{}:
d.decodeValue(rv4iptr(v), nil)
default:
// we can't check non-predefined types, as they might be a Selfer or extension.
if skipFastpathTypeSwitchInDirectCall || !fastpathDecodeTypeSwitch(iv, d) {
v := reflect.ValueOf(iv)
if x, _ := isDecodeable(v); !x {
d.haltAsNotDecodeable(v)
}
d.decodeValue(v, nil)
}
}
}
// decodeValue MUST be called by the actual value we want to decode into,
// not its addr or a reference to it.
//
// This way, we know if it is itself a pointer, and can handle nil in
// the stream effectively.
//
// Note that decodeValue will handle nil in the stream early, so that the
// subsequent calls i.e. kXXX methods, etc do not have to handle it themselves.
func (d *Decoder) decodeValue(rv reflect.Value, fn *codecFn) {
if d.d.TryNil() {
decSetNonNilRV2Zero(rv)
return
}
d.decodeValueNoCheckNil(rv, fn)
}
func (d *Decoder) decodeValueNoCheckNil(rv reflect.Value, fn *codecFn) {
// If stream is not containing a nil value, then we can deref to the base
// non-pointer value, and decode into that.
var rvp reflect.Value
var rvpValid bool
PTR:
if rv.Kind() == reflect.Ptr {
rvpValid = true
if rvIsNil(rv) {
rvSetDirect(rv, reflect.New(rvType(rv).Elem()))
}
rvp = rv
rv = rv.Elem()
goto PTR
}
if fn == nil {
fn = d.h.fn(rvType(rv))
}
if fn.i.addrD {
if rvpValid {
rv = rvp
} else if rv.CanAddr() {
rv = rvAddr(rv, fn.i.ti.ptr)
} else if fn.i.addrDf {
d.errorf("cannot decode into a non-pointer value")
}
}
fn.fd(d, &fn.i, rv)
}
func (d *Decoder) structFieldNotFound(index int, rvkencname string) {
// Note: rvkencname is used only if there is an error, to pass into d.errorf.
// Consequently, it is ok to pass in a stringView
// Since rvkencname may be a stringView, do NOT pass it to another function.
if d.h.ErrorIfNoField {
if index >= 0 {
d.errorf("no matching struct field found when decoding stream array at index %v", index)
} else if rvkencname != "" {
d.errorf("no matching struct field found when decoding stream map with key " + rvkencname)
}
}
d.swallow()
}
func (d *Decoder) arrayCannotExpand(sliceLen, streamLen int) {
if d.h.ErrorIfNoArrayExpand {
d.errorf("cannot expand array len during decode from %v to %v", sliceLen, streamLen)
}
}
func (d *Decoder) haltAsNotDecodeable(rv reflect.Value) {
if !rv.IsValid() {
d.onerror(errCannotDecodeIntoNil)
}
// check if an interface can be retrieved, before grabbing an interface
if !rv.CanInterface() {
d.errorf("cannot decode into a value without an interface: %v", rv)
}
d.errorf("cannot decode into value of kind: %v, %#v", rv.Kind(), rv2i(rv))
}
func (d *Decoder) depthIncr() {
d.depth++
if d.depth >= d.maxdepth {
d.onerror(errMaxDepthExceeded)
}
}
func (d *Decoder) depthDecr() {
d.depth--
}
// Possibly get an interned version of a string, iff InternString=true and decoding a map key.
//
// This should mostly be used for map keys, where the key type is string.
// This is because keys of a map/struct are typically reused across many objects.
func (d *Decoder) string(v []byte) (s string) {
if d.is == nil || d.c != containerMapKey || len(v) < 2 || len(v) > internMaxStrLen {
return string(v)
}
return d.is.string(v)
}
func (d *Decoder) zerocopy() bool {
return d.bytes && d.h.ZeroCopy
}
// decodeBytesInto is a convenience delegate function to decDriver.DecodeBytes.
// It ensures that `in` is not a nil byte, before calling decDriver.DecodeBytes,
// as decDriver.DecodeBytes treats a nil as a hint to use its internal scratch buffer.
func (d *Decoder) decodeBytesInto(in []byte) (v []byte) {
if in == nil {
in = []byte{}
}
return d.d.DecodeBytes(in)
}
func (d *Decoder) rawBytes() (v []byte) {
// ensure that this is not a view into the bytes
// i.e. if necessary, make new copy always.
v = d.d.nextValueBytes([]byte{})
if d.bytes && !d.h.ZeroCopy {
v0 := v
v = make([]byte, len(v))
copy(v, v0)
}
return
}
func (d *Decoder) wrapErr(v error, err *error) {
*err = wrapCodecErr(v, d.hh.Name(), d.NumBytesRead(), false)
}
// NumBytesRead returns the number of bytes read
func (d *Decoder) NumBytesRead() int {
return int(d.r().numread())
}
// decodeFloat32 will delegate to an appropriate DecodeFloat32 implementation (if exists),
// else if will call DecodeFloat64 and ensure the value doesn't overflow.
//
// Note that we return float64 to reduce unnecessary conversions
func (d *Decoder) decodeFloat32() float32 {
if d.js {
return d.jsondriver().DecodeFloat32() // custom implementation for 32-bit
}
return float32(chkOvf.Float32V(d.d.DecodeFloat64()))
}
// ---- container tracking
// Note: We update the .c after calling the callback.
// This way, the callback can know what the last status was.
// MARKER: do not call mapEnd if mapStart returns containerLenNil.
func (d *Decoder) containerNext(j, containerLen int, hasLen bool) bool {
// return (hasLen && j < containerLen) || !(hasLen || slh.d.checkBreak())
if hasLen {
return j < containerLen
}
return !d.checkBreak()
}
func (d *Decoder) mapStart(v int) int {
if v != containerLenNil {
d.depthIncr()
d.c = containerMapStart
}
return v
}
func (d *Decoder) mapElemKey() {
if d.js {
d.jsondriver().ReadMapElemKey()
}
d.c = containerMapKey
}
func (d *Decoder) mapElemValue() {
if d.js {
d.jsondriver().ReadMapElemValue()
}
d.c = containerMapValue
}
func (d *Decoder) mapEnd() {
d.d.ReadMapEnd()
d.depthDecr()
d.c = 0
}
func (d *Decoder) arrayStart(v int) int {
if v != containerLenNil {
d.depthIncr()
d.c = containerArrayStart
}
return v
}
func (d *Decoder) arrayElem() {
if d.js {
d.jsondriver().ReadArrayElem()
}
d.c = containerArrayElem
}
func (d *Decoder) arrayEnd() {
d.d.ReadArrayEnd()
d.depthDecr()
d.c = 0
}
func (d *Decoder) interfaceExtConvertAndDecode(v interface{}, ext InterfaceExt) {
// var v interface{} = ext.ConvertExt(rv)
// d.d.decode(&v)
// ext.UpdateExt(rv, v)
// assume v is a pointer:
// - if struct|array, pass as is to ConvertExt
// - else make it non-addressable and pass to ConvertExt
// - make return value from ConvertExt addressable
// - decode into it
// - return the interface for passing into UpdateExt.
// - interface should be a pointer if struct|array, else a value
var s interface{}
rv := reflect.ValueOf(v)
rv2 := rv.Elem()
rvk := rv2.Kind()
if rvk == reflect.Struct || rvk == reflect.Array {
s = ext.ConvertExt(v)
} else {
s = ext.ConvertExt(rv2i(rv2))
}
rv = reflect.ValueOf(s)
// We cannot use isDecodeable here, as the value converted may be nil,
// or it may not be nil but is not addressable and thus we cannot extend it, etc.
// Instead, we just ensure that the value is addressable.
if !rv.CanAddr() {
rvk = rv.Kind()
rv2 = d.oneShotAddrRV(rvType(rv), rvk)
if rvk == reflect.Interface {
rvSetIntf(rv2, rv)
} else {
rvSetDirect(rv2, rv)
}
rv = rv2
}
d.decodeValue(rv, nil)
ext.UpdateExt(v, rv2i(rv))
}
func (d *Decoder) sideDecode(v interface{}, basetype reflect.Type, bs []byte) {
// NewDecoderBytes(bs, d.hh).decodeValue(baseRV(v), d.h.fnNoExt(basetype))
defer func(rb bytesDecReader, bytes bool,
c containerState, dbs decByteState, depth int16, r decReader, state interface{}) {
d.rb = rb
d.bytes = bytes
d.c = c
d.decByteState = dbs
d.depth = depth
d.decReader = r
d.d.restoreState(state)
}(d.rb, d.bytes, d.c, d.decByteState, d.depth, d.decReader, d.d.captureState())
// d.rb.reset(in)
d.rb = bytesDecReader{bs[:len(bs):len(bs)], 0}
d.bytes = true
d.decReader = &d.rb
d.d.resetState()
d.c = 0
d.decByteState = decByteStateNone
d.depth = 0
// must call using fnNoExt
d.decodeValue(baseRV(v), d.h.fnNoExt(basetype))
}
func (d *Decoder) fauxUnionReadRawBytes(asString bool) {
if asString || d.h.RawToString {
d.n.v = valueTypeString
// fauxUnion is only used within DecodeNaked calls; consequently, we should try to intern.
d.n.s = d.stringZC(d.d.DecodeBytes(nil))
} else {
d.n.v = valueTypeBytes
d.n.l = d.d.DecodeBytes([]byte{})
}
}
func (d *Decoder) oneShotAddrRV(rvt reflect.Type, rvk reflect.Kind) reflect.Value {
if decUseTransient &&
(numBoolStrSliceBitset.isset(byte(rvk)) ||
((rvk == reflect.Struct || rvk == reflect.Array) &&
d.h.getTypeInfo(rt2id(rvt), rvt).flagCanTransient)) {
return d.perType.TransientAddrK(rvt, rvk)
}
return rvZeroAddrK(rvt, rvk)
}
// --------------------------------------------------
// decSliceHelper assists when decoding into a slice, from a map or an array in the stream.
// A slice can be set from a map or array in stream. This supports the MapBySlice interface.
//
// Note: if IsNil, do not call ElemContainerState.
type decSliceHelper struct {
d *Decoder
ct valueType
Array bool
IsNil bool
}
func (d *Decoder) decSliceHelperStart() (x decSliceHelper, clen int) {
x.ct = d.d.ContainerType()
x.d = d
switch x.ct {
case valueTypeNil:
x.IsNil = true
case valueTypeArray:
x.Array = true
clen = d.arrayStart(d.d.ReadArrayStart())
case valueTypeMap:
clen = d.mapStart(d.d.ReadMapStart())
clen += clen
default:
d.errorf("only encoded map or array can be decoded into a slice (%d)", x.ct)
}
return
}
func (x decSliceHelper) End() {
if x.IsNil {
} else if x.Array {
x.d.arrayEnd()
} else {
x.d.mapEnd()
}
}
func (x decSliceHelper) ElemContainerState(index int) {
// Note: if isnil, clen=0, so we never call into ElemContainerState
if x.Array {
x.d.arrayElem()
} else if index&1 == 0 { // index%2 == 0 {
x.d.mapElemKey()
} else {
x.d.mapElemValue()
}
}
func (x decSliceHelper) arrayCannotExpand(hasLen bool, lenv, j, containerLenS int) {
x.d.arrayCannotExpand(lenv, j+1)
// drain completely and return
x.ElemContainerState(j)
x.d.swallow()
j++
for ; x.d.containerNext(j, containerLenS, hasLen); j++ {
x.ElemContainerState(j)
x.d.swallow()
}
x.End()
}
// decNextValueBytesHelper helps with NextValueBytes calls.
//
// Typical usage:
// - each Handle's decDriver will implement a high level nextValueBytes,
// which will track the current cursor, delegate to a nextValueBytesR
// method, and then potentially call bytesRdV at the end.
//
// See simple.go for typical usage model.
type decNextValueBytesHelper struct {
d *Decoder
}
func (x decNextValueBytesHelper) append1(v *[]byte, b byte) {
if *v != nil && !x.d.bytes {
*v = append(*v, b)
}
}
func (x decNextValueBytesHelper) appendN(v *[]byte, b ...byte) {
if *v != nil && !x.d.bytes {
*v = append(*v, b...)
}
}
func (x decNextValueBytesHelper) bytesRdV(v *[]byte, startpos uint) {
if x.d.bytes {
*v = x.d.rb.b[startpos:x.d.rb.c]
}
}
// decNegintPosintFloatNumberHelper is used for formats that are binary
// and have distinct ways of storing positive integers vs negative integers
// vs floats, which are uniquely identified by the byte descriptor.
//
// Currently, these formats are binc, cbor and simple.
type decNegintPosintFloatNumberHelper struct {
d *Decoder
}
func (x decNegintPosintFloatNumberHelper) uint64(ui uint64, neg, ok bool) uint64 {
if ok && !neg {
return ui
}
return x.uint64TryFloat(ok)
}
func (x decNegintPosintFloatNumberHelper) uint64TryFloat(ok bool) (ui uint64) {
if ok { // neg = true
x.d.errorf("assigning negative signed value to unsigned type")
}
f, ok := x.d.d.decFloat()
if ok && f >= 0 && noFrac64(math.Float64bits(f)) {
ui = uint64(f)
} else {
x.d.errorf("invalid number loading uint64, with descriptor: %v", x.d.d.descBd())
}
return ui
}
func decNegintPosintFloatNumberHelperInt64v(ui uint64, neg, incrIfNeg bool) (i int64) {
if neg && incrIfNeg {
ui++
}
i = chkOvf.SignedIntV(ui)
if neg {
i = -i
}
return
}
func (x decNegintPosintFloatNumberHelper) int64(ui uint64, neg, ok bool) (i int64) {
if ok {
return decNegintPosintFloatNumberHelperInt64v(ui, neg, x.d.cbor)
}
// return x.int64TryFloat()
// }
// func (x decNegintPosintFloatNumberHelper) int64TryFloat() (i int64) {
f, ok := x.d.d.decFloat()
if ok && noFrac64(math.Float64bits(f)) {
i = int64(f)
} else {
x.d.errorf("invalid number loading uint64, with descriptor: %v", x.d.d.descBd())
}
return
}
func (x decNegintPosintFloatNumberHelper) float64(f float64, ok bool) float64 {
if ok {
return f
}
return x.float64TryInteger()
}
func (x decNegintPosintFloatNumberHelper) float64TryInteger() float64 {
ui, neg, ok := x.d.d.decInteger()
if !ok {
x.d.errorf("invalid descriptor for float: %v", x.d.d.descBd())
}
return float64(decNegintPosintFloatNumberHelperInt64v(ui, neg, x.d.cbor))
}
// isDecodeable checks if value can be decoded into
//
// decode can take any reflect.Value that is a inherently addressable i.e.
// - non-nil chan (we will SEND to it)
// - non-nil slice (we will set its elements)
// - non-nil map (we will put into it)
// - non-nil pointer (we can "update" it)
// - func: no
// - interface: no
// - array: if canAddr=true
// - any other value pointer: if canAddr=true
func isDecodeable(rv reflect.Value) (canDecode bool, reason decNotDecodeableReason) {
switch rv.Kind() {
case reflect.Ptr, reflect.Slice, reflect.Chan, reflect.Map:
canDecode = !rvIsNil(rv)
reason = decNotDecodeableReasonNilReference
case reflect.Func, reflect.Interface, reflect.Invalid, reflect.UnsafePointer:
reason = decNotDecodeableReasonBadKind
default:
canDecode = rv.CanAddr()
reason = decNotDecodeableReasonNonAddrValue
}
return
}
func decByteSlice(r *decRd, clen, maxInitLen int, bs []byte) (bsOut []byte) {
if clen == 0 {
return zeroByteSlice
}
if len(bs) == clen {
bsOut = bs
r.readb(bsOut)
} else if cap(bs) >= clen {
bsOut = bs[:clen]
r.readb(bsOut)
} else {
var len2 int
for len2 < clen {
len3 := decInferLen(clen-len2, maxInitLen, 1)
bs3 := bsOut
bsOut = make([]byte, len2+len3)
copy(bsOut, bs3)
r.readb(bsOut[len2:])
len2 += len3
}
}
return
}
// decInferLen will infer a sensible length, given the following:
// - clen: length wanted.
// - maxlen: max length to be returned.
// if <= 0, it is unset, and we infer it based on the unit size
// - unit: number of bytes for each element of the collection
func decInferLen(clen, maxlen, unit int) int {
// anecdotal testing showed increase in allocation with map length of 16.
// We saw same typical alloc from 0-8, then a 20% increase at 16.
// Thus, we set it to 8.
const (
minLenIfUnset = 8
maxMem = 256 * 1024 // 256Kb Memory
)
// handle when maxlen is not set i.e. <= 0
// clen==0: use 0
// maxlen<=0, clen<0: use default
// maxlen> 0, clen<0: use default
// maxlen<=0, clen>0: infer maxlen, and cap on it
// maxlen> 0, clen>0: cap at maxlen
if clen == 0 || clen == containerLenNil {
return 0
}
if clen < 0 {
// if unspecified, return 64 for bytes, ... 8 for uint64, ... and everything else
clen = 64 / unit
if clen > minLenIfUnset {
return clen
}
return minLenIfUnset
}
if unit <= 0 {
return clen
}
if maxlen <= 0 {
maxlen = maxMem / unit
}
if clen < maxlen {
return clen
}
return maxlen
}